Castered dual wheel assembly



Sept. 22, 1959 r. c. DELKER ET AL cAsTERED DUAL WHEEL ASSEMBLY Filed Deo. 3l, 1953 nited States Patent CASTERED DUAL WHEEL ASSEMBLY Thomas C. Delker and William J. Eaton, South Bend, Ind., assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application December 31, 1953, Serial No. 401,643

l12 Claims. (Cl. 301-36) This invention relates to a castered dual wheel assembly for aircraft and more particularly to a castered dual wheel assembly employing independently rotatable wheels in combination with a shimmy damper.

It is a well-known practice to caster or pivot the nose wheel of a tricycle aircraft landing gear about an axis which is inclined forward at a small angle to the vertical. A wheel of this sort is known to be torsionally unstable and has an undesirable tendency to shimmy or oscillate about its castering axis upon movement over ground surfaces. In an eort to combat this tendency certain special wheel arrangements have heretofore been employed. For example, co-rotating dual wheels have been used to stabilize the strut. Although eiiective for stabilization purposes, co-rotating dual wheels in the nose position make ground steering diiicult and cause the tires to scrape or scrub on the ground whenever the wheels change their direction of movement. Other special wheel arrangements heretofore employed have proved to be lacking in eiectiveness or simplicity.

' As will become apparent from Athe following description, we have provided a dual wheel assembly which is: (l) torsionally stable as it passes over ground surfaces, (2) unimpaired in ground steering, and (3) simple and lightweight in construction. Briey, this result is accomplished by employing a pair of independently rotatable dual wheels which prevent tire scrubbing in combination with a shimmy damping device which prevents the aforesaid wheel oscillation. The wheels of the present invention are carried on bearings which are disposed outside the wheel rims in contrast to the conventional wheel which employs centrally disposed bearings. It will 1 be seen that by this method of construction the shimmy damping device can be conveniently carried within the dual wheel configuration thereby providing a simple, compact assembly.

Another object of the invention lies in the provision of a viscous type shimmy damper which utilizes the relationship of the velocity of a moving surface to iluid resistance in arresting shimmy. The above and other objects and features of the invention will become apparent from the following description taken in connection with the accompanying drawing wherein the single figure illustrates the subject matter of the invention in cross-section.

Referring to the drawing, the lower or inner cylinder 10 of a telescoping shock strut is shown as having an t Journaled within housing 12 and on each side of a large diameter outer rim 24 and a reduced diameter sec- .f

tion 26 on its axial inboard side formed for insertion into Y 2,905,505 Patented Sept. 22, 1959 ICC the inner race of one of bearings 16 or 18. The outer flanges of the wheels are demountable to facilitate application and removal of a tire and comprise an annular tire retaining flange 28 and a flange retaining ring 30. Ring 30 is split at one point in its circumference in order that it may be snapped into annular groove 32 after flange 28 is slipped onto rim 24. In its assembled position, the lip or bead of the tire will lie on extension 34 of ilange 28.

In order to hold annular shoulder 35 of each wheel in abutment with its respective bearing, a cylindrical fastening element 36 is provided. Element 36 is carried for rotational movement on wheel 20 by plate 38 and a series of fastening members 40. At the opposite end of element 36 is a radial flange 42. A roller thrust bearing 44 is carried between flange 42 and the reduced diameter section 26 of wheel 22 to thereby permit relative rotation of the wheels with respect to each other. Retaining nut 46 is threadedly received on the left end of element 36 to draw ange 42 snugly against bearing 44.

Note that in the construction shown support for the wheel rim comes from the side in cantilever fashion rather than from the axle as it does in a conventional Wheel. Thus, a central axle becomes unnecessary, and the hub and spoke sections of the wheels can be eliminated. The taper on bearings 16 and 18 is such that the forces on the wheels tending to produce a moment which will force the upper portion of the wheel inward against its associated bearing are minimized, the greater part of the forces being taken along a line perpendicular to the roller axis.

` Axial outward thrusts on the bottom portions of the wheels due to the aforesaid cantilever loading will be taken by thrust bearing 44.

Due to the well-known inherent instability in a castered wheel arrangement, cylinder 10 and wheels 20 and 22 will oscillate or shimmy about the cylinder axis upon movement of the wheels over the ground surface. This oscillation will cause a resultant high frequency, differ-` ential rotation inthe wheels. In order to prevent'or damp the diierential rotation and coincident oscillation of the wheels, la shimmy damper assembly, generally indicated at 48, is mounted within the dual wheel assembly. The axis of the shimmy damper assembly 48 a'nd the axis of the cylinder 10 lie in a common plane at right angles to each other.

Therdamper assembly includes a plate Si) which is bolted to wheel 22 by bolts 52 and an axially extending shaft or torque-taking member 54. One end of member 54 is secured to plate 50 and the other end is rotatably carried within a bearing 56 which is iitted into one end of the cylindrical fastening element 36. Member 54 is splined to receive a rst stack of disc-like elements 58 which are rotatable with wheel 22; and element 36 is internally splined to receive a second stack of disc-like elements 60 which are interleaved with elements 58 and rotatable with wheel 20. An end cap 62 is threadedly received on the right end of element 36 to form a closed cylinder chamber 64 within which the disc-like elements are carried. The cylinder chamber contains a high viscosity iluid which occupies the spaces between the respective stacks of disc-like elements.

It will be noted that as long as wheels 20 and 22 rotate at the same velocity there will be no relative rotation between the respective stacks of disc-like elements. However, when the wheels begin to oscillate, the aforesaid high frequency differential rotation of the wheels and their associated stacks will result. This oscillation will be damped and nally stopped by the high resistance offered to the stacks by the iluid in chamber 64. Since the resistance offered to a moving surface in a iluid of a given viscosity is proportional to the velocity of the surface, a viscosity can be chosen which will offer high resismnce vtor-high frequency-:differential rotation and low I' resistanceto. gradualrotaton.` Thus, whenthe wheels t turn on the ground so that one wheel must travel a greater distance than the other, the resultant gradual relativerotati'on ,of the wheels and stacks :will not. beisappre clably restricted.: Thewheels will,.therefore,=.turn Omthe ground without scraping.

Although only one embodiment-of'our invention has beenA shown and described in detail,'it is to:be understood that various changesin. number and arrangement of .parts can be-made to suit requirements.

Having thusdescribed our invention, .what we claim as new and desire to secure by Letters Patent is:

l. .Adualwheel assembly for use 'with'aswiveled aircraft shockv strutcomprising a circularfbearing'-housing carried at the lower lextremity of said strut, a'pairiof'independent .bearings .carried within said housing` andA tapered so as to takeaxial inward thrusts, a1. wheel-,rotatably mountedoneach of said bearings,said.wheel comprising an, outer arim' portion having a reduceddiameterfsection at onesideformed for abutment with the inner 4periphery of 1ts associated bearing, atubular member fastened to one of said wheels andv carried within said-.reduced-diameter' sections for drawing said wheels togetherv in. abutment with ,their respectivetbearings to. thereby lock the wheels against axial'movement, said` tubular member having a radial flangeat each end inadjacent relationship. with one of said reduced diameterA sections, av bearing intervl posed betweenv one ofsaid flangesand the,reduceddiam-. eter: section ofthe other of saidwheelsto-allow differential-rotationiof thewheels, and means carriedwithin'said tubular Vmember for. damping highfrequency `differential rotationof the wheels, said means comprising av centrally disposed torque-taking member fastened; to said other wheeland extending .through said tubular member, a/iirst stack of axiallyv spaced co-axially disposed annulanmembers carried by said torque-taking.; member,y a.- second stack of axially spaced coraxially disposed annular memberscarried by saidtubular member ininterleaving. relaf tionshipfwith said rst stack, and a, highi viscosity fluid carried in thespace between the respective stacks;.which will offer highresistance torapiddiierential rotation; of the annular members but low resistanceto gradual differentialrotation.

2;. Azdualwheelassembly for use witha swiveledairf craftfshoekstrut comprising a circular bearing housing carried at the lower extremity ofsaid struta pair-loting dependent bearings carriedV within said; housing andtaf pered so as to take axial inward` thrusts, awheeLrotat-` ably mounted on each of said bearings,lsadwh.eel comprising an outerrim portion having areduced diameter section at one. side formed for abutment withthe inner periphery of. its associatedbearingmeans fastened to one of said wheelsfor. drawing the. wheels together; in abutmentzwith their respective hearings.A to therebyflock the wheels against axial movement, said means allowing differential rotation of thewheels, and means associated with said first-mentioned means for damping high frequency differential rotation of thewheels, said damping means` comprising a stack of axially spaced. co-axially disposed annular members carried byv oneof said wheels, another stack of axially spaced co-axially-disposed annular members carried by the other of. said wheelsinpinter.- leaving relationship with said first stack, anda. highlvisf cosity uid carried in the space betweenthe; respective stacks which will offer high. resistance to. rapid, intermittent differential rotation of the annular members but low resistance to gradual rotation.

i 3. A dual wheel and. tire assembly for use. with a swiveled aircraft shock strut comprising a circular; bearing housing carried at the lower extremity ofsaid strut, a pair of independent bearings carried withinsaid housing, awheel rotatably mounted on each of said bearings, said wheel comprising a one-piece outer rim portion having a reduced diameter sectionY at its one side formed for abutment with the inner periphery of one of saidbearings and a removable, flange at ,its other side toA facilitate `removal. of a tire from the rim, a fastening element carried within said reduced diameter sections for locking said wheels against axial movement, means permitting independent rotation of said wheels about their respective bearings, and means arranged betweenl said wheels and surrounded by said housing for damping intermittent, high frequency diiferentialt-rotation of, 'the wheels, said damping. means comprising .a iirst stack of axially spaced co-axially dis-Y posed, discglike elementsrtatable with one of said wheels, a second stack of ,axially spaced `col-,axially ,disposed .disclike elements rotatable lwith the other of said Awheels in interleaving relationJ with vsaid iirst stack, and :arsixbstance carried in the space between theuresplective stacks which will offer high resistance to rapid, intermittent different rotation of the disc-like elements but low resistance to gradual rotation.

4. Adual wheel assembly fonuse witha 1swiveled aircraft. shock. strut comprising acircular bearingv housing carried at the lower .extremityof 1said strut, a pair of inde: pendent bearings carried ,within said housing, a pair-of independently rotatable wheels mountedon said bearings, meansifor holding vsaidwheels againstaxial movement,A and' means disposed between said wheels and surrounded by. said housing. for damping intermittent, high frequency differential rotation of 'the.wheels, said lattermentioned means comprising-a irststack of axiallyv spaced 4cri-axially disposed'disc-likeelements rotatablek withlone of said wheels, atsecond stack. of axially` spaced co-axially.- disg posed disc-like elements rotatablewiththe o thenof said wheelsin interleaving relationship-with said iirststacl, andra iiuicl carriedin the. space between said stacks and having a viscosity which will offer high resistance to rapid, intermittent differential rotation1ofl the disc-like elements but lowresistance to gradual differential rotation.

5. A' dual wheel assembly-forusewith a swiveledair` craft shock strut comprising apair ofi independently ro; tatable wheels carried at the lower. extremityy of said strut. and damping means locatedbetween adjacentend portionstofsaid wheels .combinedfwith each of said wheels to exert substantially equally retarding action. thereon to dampen intermittent, high frequency; ditferentialrotation ofv the-wheels, said means comprisinga rstl stach-of axially f spaced co-axially disposed; disc-like f elements. ro;l tatable with one of said wheels, a second stacl;;ofaxially spaced co-.axially disposed vdisc-like elementsrotatable withthe other of4 said wheels ininterleaying relationship with said rst, stack, andra iiuigl,charriedwin theA space betweensaid stacks. Which will offer highlresistanceto rapid, intermittent differential rotation; ofV the disc-like elements. but low resistance to gradpal differential rotation.

6. A dual hubless wheel assemblyA fon use, a swiveledaircraft shock strut.comprising a pairA of independently rotatable wheels carried atthe.I lower extremity ofsaid strut, and means disposedrk between said .wheels and provided at the end of saidistrut inline with-the. axis thereof for damping intermittenti,highfrequency differ-l ential rotationl of the wheels, and comprising a surface rotatable with one of said wheel sa companion surface rotatable with therother of said wheelsin adjacent relationship to the surface rotatable with; said one wheel, and a high. viscosity fluid carried in the space betweensaid surfacesA which will damp said. intermittenthigh fr equency differential rotationbut permitgradual-rptationof the wheels.

7. A dual wheel assembly'foruse witha swiveledaircraft shock strut. comprisinga pairofindependently rotatable hublesstwheels carriedv at; the lowerextremity of said strut, and means disposedjbetweemsaid wheelsV with its axis located at right angles to and in thesame plane as the axis of said strut for damping internjiittent, high frequencydifferential rotationofthe wheelsand comprising a first pluralityl of elements rotatable with one ofsaid i i i l wheels, a second plurality of elements rotatable with the other of said wheels in interleaving relation with said rst plurality, and a high viscosity fluid carried in the space between the respective pluralities.

8. A dual wheel and tire assembly for use with a swiveled aircraft shock strut comprising a circular bearing housing carried at the lower extremity of said strut, a pair of independent bearings carried within said housing and tapered to take axial inward thrusts, a wheel rotatably mounted on each of said bearings, said wheel comprising a one piece outer rim portion having a reduced diameter section at one side formed for abutment with the inner periphery of its associated bearing, a pair of radially outwardly extending anges carried by said rim, one of said flanges being removable to facilitate application of a tire to said rim, a tubular member fastened to one of said wheels and carried within said reduced diameter sections for drawing said wheels axially inwardly against their respective bearings, said tubular member having a radial ange at each end in adjacent relationship with one of said reduced diameter sections. and a Abearing interposed between one of said anges and the reduced diameter section of the other of said wheels to take axial outward thrusts and to allow differential rotation of the wheels.

9. A dual wheel assembly for use with a swiveled aircraft shock strut comprising a circular bearing housing carried at the lower extremity of said strut, a pair of independent bearings carried within said housing and tapered so as to take axial inward thrusts, a wheel rotatably mounted on each of said bearings, said wheel comprising an outer rim portion having a reduced diameter section at one side formed for abutment with the inner peripheral surface of its associated bearing, and means for drawing said wheels axially inwardly against their respective bearings, said means comprising a cylindrical member having its one end fastened to one of said wheels and its other end flanged, and a bearing interposed between the reduced diameter section of the other wheel and said hanged 6 end to thereby permit independent rotation of the wheels about their respective bearings.

l0. A dual wheel assembly for use with a swiveled aircraft shock strut comprising a circular bearing housing carried at the lower extremity of said strut, bearing means carried within said housing, a pair of independently rotatable wheels carried by said bearing means, and means for locking said wheels together against axial movement including coupling means passing between said wheels, and an antifriction bearing which allows relative rotational movement between turnable portions of said coupling means.

11. A dual wheel assembly comprising vertically supported bearing means, a pair of hubless, tire-supporting rims each of which is independently rotatable on the `inner periphery of said bearing means and means for interlocking said wheels axially and including antifriction means permitting independent rotation of said wheels.

12. The combination with a wheel supporting structure having a bearing housing, of a pair of wheels arranged with their axes coincident, one wheel carried on each side of said housing, a pair of bearings in the housing, one for each wheel, each bearing arranged to take radial and axial thrusts, each wheel being provided with an axial extending portion of reduced diameter for receiving its associated bearing, means tieing the reduced diameter portions of said wheels together for relative rotation, and a mechanism controlling relative rotation between said wheels including interleaving elements carried by each wheel and immersed in a high viscosity fluid.

References Cited in the tile of this patent UNITED STATES PATENTS 2,514,137 OConnor July 4, 1950 2,620,235 Butler Dec. 2, 1952 2,644,654 Mercier July 7, 1953 FOREIGN PATENTS 985,509 France Mar. 14, 1951 Attesting Oicer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nm.A 23057505; September 22?. 1959 vThomas C. .Delker et aL,

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. y

Column 4Y line 40, after "fstrut insert a Comma.

Signed and sealed this 13th day of September 1960.

(SEAL) Attest:

KARL H. AXLINE` ROBERT C. WATSON Commissioner of Patents 

